Friction draft gear

ABSTRACT

The disclosure relates to a friction draft gear of the type shown in U.S. Pat. No. 2,496,442 in which a supplemental resistance arrangement is interposed between the friction shoe and the closed wall of the gear casing in the form of a flat spring seat engaging the shoes, a pedestal engaging the casing closed end, and a tubular butyl rubber member received between the spring seat and the pedestal with all three being received within and spaced from a helical spring that is applied between the shoes and the casing closed wall and parallel with the helical spring.

United States Patent [72] Inventor Bertil E. Peterson Chicago, Ill. [21) Appl. No. 857,881 [22] Filed Sept. 15, 1969 [45] Patented June 1, 1971 [73] Assignee Cardwell Westinghouse Company [54} FRICTION DRAFT GEAR 9 Claims, 5 Drawing Figs.

[52] US. Cl. 213/34, 213/22, 213/40 [51] Int. Cl 361g 9/06, B61 g 9/14 501 Field of Search 213 22, 34, 40, 40 D, 45, 43; 267/63 [56] References Cited UNITED STATES PATENTS 2,496,442 2/1950 Cardwell 213/34 2,649,973 8/1953 Clark et all 213/34 2,956,692 lO/l960 Campbell 213/34 3,178,036 4/1965 Cardwell 213/40 3,379,318 4/1968 Trongeau 213/22 Primary ExaminerDrayton E. Hoffman Attorney-Mann, Brown, McWilliams & Bradway ABSTRACT: The disclosure relates to a friction draft gear of the type shown in US. Pat. No. 2,496,442 in which a supplemental resistance arrangement is interposed between the friction shoe and the closed wall of the gear casing in the form of a flat spring seat engaging the shoes, a pedestal engaging the casing closed end, and a tubular butyl rubber member received between the spring seat and the pedestal with all three being received within and spaced from a helical spring that is applied between the shoes and the casing closed wall and parallel with the helical spring.

PATENTEDJUN 11911 3,581,909

sum 1 or 3 \NVENTOR BERTIL E PETERSON ATTORNEYS FRICTION DRAFT GEAR This invention relates to railroad car draft gear of the friction type and more particularly to an improvement in the friction draft gear arrangement shown in Cardwell U.S. Pat. No. 2,496,442.

In the arrangement of said patent, the casing has open and closed opposed ends and defines a friction chamber at the casing open end in which is mounted a keen angle friction assembly including friction shoes that are engaged for thrust purposes by an articulated cluster of wedge members that are in turn engaged by a self-adjusting thrust member that is actuated by the gear follower. The load response of the shoes in resisted by helical springs interposed between the shoes and the casing closed end, with the thrust member being held against ejection from the casing and at a predetermined riding position by an assembly bolt that extends through the casing along its axial center.

This draft gear was designed for and has been used in l8lrinch draft gear pockets, and provides about 18,500 ft./lbs. capacity with Zia-inches of travel.

A principal objectof this invention is to provide a draft gear of the type shown in said patent that is applicable to a 17 inch pocket and will provide on the order of 22,000 ft./lbs. capacity with the same travel even though the gear itself must be correspondingly shorter than when designed for l8%-inch pockets.

Another principal object of the invention is to provide a supplemental resistance arrangement for friction draft gear of the type indicated involving a helical spring and tubular core of rubber or equivalent material that act in substantially independent parallel spaced-apart relation between the gear friction shoes and its casing closed end without the core buckling or becoming pinched between the coils of the spring.

Other objects of the invention are to provide a draft gear especially suited for short draft gear pockets that is economical of manufacture, convenient to install, and long lived in use.

Still other objects, uses and advantages will be obvious or become apparent from a consideration of the following detailed description and the application drawings.

In the drawings:

FIG. 1 is a longitudinal sectional view through a draft gear pocket equipped with a draft gear in accordance with this invention, with one half of the gear being shown in plan;

H6. 2 is an enlarged longitudinal sectional view of the tubular core member that is employed in the draft gear of FIG. 1, in accordance with this invention;

FIG. 3 is a side elevational view of the draft gear shown in H6. 1, with the upper half of the draft gear being shown in section;

FIG. 4 is a view similar to that of FlG. 3 but showing the draft gear compressed after its travel stroke has been completed; and

FIG. 5 is a force vs. closure curve illustrating the advantages of this invention.

However, it is to be understood that the specific drawings that are provided are supplied primarily to comply with the requirements of the Patent Code, and that the invention may have other embodiments that will be obvious to those skilled in the art without departing from the spirit and scope of the invention.

Referring now to F I68. 1 and 2, reference numeral generally indicates the draft gear mounted within a draft gear pocket 12 of the shortened 17 inch length, which is defined by the center sills l4 and 16 of the car and the spaced sets of draft gear lugs 18 and 20.

The draft gear comprises a housing or casing 22 having a closed end 24 and an open end 26. Adjacent the open end 26 of the housing or casing 22 the housing or casing defines a friction chamber 28 defining friction surfaces 30 that are slidably engaged by friction shoes 32 which are operably engaged by a cluster 34 of articulated wedge members 36 that are in turn operably engaged by a self-adjusting thrust member 38 which is in turn engaged by the conventional follower 40 that is interposed between the draft gear l0 and the draft gear lugs 20.

Movement of the shoes 32 inwardly of the draft gear is resisted by helical spring 42 that is interposed between the rear or base wall 24 of the draft gear housing and the shoes 32, spring 32 engaging the fiat undersurfaces 44 of the shoes and surface 25 of wall 24.

As assembly bolt 46 extends between the thrust member and a boss structure 48 that is defined by the housing rear wall 24, the head 50 of the bolt being seated in the boss structure 48 and its threaded end 52 extending fowardly through the thrust member 38 for application of washer 54 and nut 56.

Boss structure 48 in the embodiment illustrated comprises an annular inwardly directed flange wall 57 that is'open as at 59 on opposed sides thereof and defines an annular rim 61 that is engaged by bolt head 50.

Draft gear 10 is embraced by yoke 60 which is connected to coupler 62 by suitable draft key 64 in the well-known manner.

In the particular articulated wedge member cluster 34 that is illustrated, one of the wedge members 36 is integral with a core structure 65 in accordance with the embodiment of FIGS. 6-10 of said patent, the disclosure of which may be referred to for the specifics of the friction assembly illustrated, though it may be mentioned that for each draft gear the friction shoes are three in number, as are the wedge members and friction chamber 28 is polygonal in configuration.

In accordance with this invention, the inner helical spring of said patent is eliminated and there is substituted therefor a supplemental resistance device 70 which comprises a special tubular core member 72 that is interposed between a pedestal 74 seated against the casing rear wall over the boss structure 48 and a fiat spring seat 76 against which the flat undersurfaces 44 of the friction shoes engage.

The pedestal 74 is in the form of a cup-shaped member 78 defining an annular sidewall 80 and an end wall 82 formed to define opening 84 through which the bolt 46 extends. The pedestal 74 is proportioned to loosely fit over the boss structure 48 and have its sidewall 80 spaced from the coils of spring 42 about an eighth of an inch when the pedestal is centered within the gear.

The pedestal 74 defines a flat or annular surface that is engaged by the end 92 of the core member 72, while the end 94 of the core member engages flat or planar surface 96 of spring seat 76. Spring seat 76 is an annular member shaped to define the surface 96 and an opposed planar or flat surface 98 against which the surfaces 44 of friction shoes seat. Member 76 defines central opening 100 through which the assembly bolt 46 extends.

The members 74 and 76 are formed from a suitable metallic substance such as cast steel. The outwardly facing surface 102 of the pedestal and the corresponding surface 104 of the spring seat have approximately the same diameters.

The tubular member 72 is formed from a suitable natural or synthetic rubber or its equivalent, and butyl rubber is preferred. The core member 72 comprises a tubular element having a bore 112 (see FIG. 2) defined by inner cylindrical surface 114 which is cylindrical throughout its length, which bore 112 receives the assembly bolt 46. Body 110 defines flat annular end surfaces 116 and 118 that engage the pedestal 74 and spring seat 76, respectively.

The outer surface 120 of the body 110 is formed to define a cylindrical portion 122 and a frustoconical portion 124 that merges into the cylindrical portion at 126. Frustoconical sur face 124 tapers inwardly of the body 10 and of the draft gear casing in the direction of end surface 118. The diameter of the surface 122 is substantially equivalent to the diameters of surfaces 102 and 104 of the pedestal and spring seat respectively.

As indicated, the core 72 is preferably formed frombutyl rubber, and preferably this material should have a shore A hardness of 72-77, a tensile of 2,000 psi. (minimum), an elongation of 275 per cent minimum to 400 percent maximum, 200 percent modulus-950 p.s.i. (minimum) with set at break of 20 percent (maximum).

In the assembled condition of the gear 10, the supplemental resistance device 70 and helical spring 42 are each under approximately equal pressures of 6,000 pounds each. A core member 72 in the unstressed state is about 5 Aa-inches long and is compressed to about 4"/s-inches in the assembled, normal riding condition of the gear. In the riding position of the gear, the surfaces 44 of the friction shoes 32 are spaced from the surface 25 of end wall 24 by a distance of approximately 9 inches, meaning that the core member 72 spans about 55 percent of the distance between the friction shoes 32 and the surface of end wall 24 in the riding position of the gear.

The surface 122 of the core member 72 has a diameter of 4% inches while the surface 114 of the core member has a diameter of 2 inches. In the unstressed condition of the core member 72, the cylindrical surface 122 has a length of 2%- inches longitudinally of the core member while the surface 124 has a length of Zia-inches longitudinally of the core member and terminates in a rounded corner 120 that has a diameter of 3%-inches.

The parts of the draft gear are arranged such that at full closure the supplemental resistance device 70 and the coil spring 42 in combination shall provide a resistance pressure that is 530 percent greater than the combination of these two devices at the neutral or riding condition of the gear. At full closure, core member 72 will provide a resistance pressure that is 300 percent greater than that provided by spring 42 alone.

It will be observed that the diameter of surface 122 of core member 72 is approximately 2.l times the diameter of internal surface 114. In the riding position of the gear, the length of the core member 72 will be in excess of the ZYr-inch travel of the gear by 220 percent.

When the gear is in its assembled relation, it is applied to the draft gear pocket 12 to the position indicated in HO. 1 in any suitable manner and in association with yoke 60 and coupler 62 following conventional practices. Gear is thus arranged to cushion both buff and draft forces, and when a buff force is applied to the coupler 62, follower 40 moves to the left of lugs to force the thrust member 38 inwardly of the draft gear casing 22, whereby the cluster 34 of wedge members are all tightened together into a compact metal hedge for pressure transmission to the friction shoes 32. Because of the keen angles at which the thrust assembly transmits pressure to the friction shoes, the radially outward pressure against the friction shoes is exceptionally high and the radial pressure is increased to tremendous magnitudes by the inward crowding of the friction shoes as they are forced longitudinally along the tapered frictional walls 30 of the chamber 28 to the left of FIG. 1.

This movement is opposed by helical spring 42 and the supplemental resistance device 70, these parts contracting from the position of FIG. 3 to the position of H6. 4 as the gear moves toward full closure. The parts associated with the supplemental resistance device 70 are so proportioned that at full closure, the volume of the core member 72 is made substantially the same as the space between the pedestal surface 90, the spring seat surface 96, the assembly bolt 46, and the inner diameter of the helical spring 42, without the material of the core being appreciably squeezed out between the coils of the spring 42.

As the gear goes through its closure structure, device 70 and spring 42 function independently of each other but act in parallel resisting inward movement of the friction shoes 32.

On release, the reverse action occurs with the arch supported by the thrust member 38 collapsing and the resistance forces provided by the spring 42 and supplemental resistance device 70 on the friction shoes moving the friction assembly to the initial riding position of FIGS. 1 and 3.

Referring to FIG. 5, it will be observed that the curve labeled 130 represents the familiar pressure travel characteristic of the helical spring alone while the curve labeled 132 represents the characteristic of the combination of helical spring 42 and supplemental resistance device 70. The dramatic increase in capacity provided by the combination indicated is self-evident from the drawing.

Draft impacts are cushioned in the same manner, though in draft the yoke 60 biases housing 22 in the direction of lugs 20 to urge thrust member 38 inwardly of housing 22 in the manner indicated. The self-adjusting feature of thrust member 38 has to do with its ability to change position with follower 40 as the coupler swings to various angles relative to the longitudinal axis of the car.

The foregoing description and the drawings are given merely to explain and illustrate the invention and the invention is not to be limited thereto, except insofar as the appended claims are so limited, since those skilled in the art who have the disclosure before them will be able to make modifications and variations therein without departing from the scope of the invention.

1 claim:

1. In the draft gear for mounting in the draft gear pocket of a railroad car and including a casing forming a friction chamber defining friction walls, friction shoes in sliding engagement with the walls, said casing having open and closed ends, a self-adjusting thrust member adjacent the casing open end cooperating with an articulated cluster of wedge members for transmitting load forces to the shoes, and resilient means for resisting the load response movement of said shoes including a coil spring seated between the casing closed wall and the shoes, and an assembly bolt extending axially of the gear between said thrust member and an inwardly extending boss formed in said casing closed end, the improvement wherein:

supplemental resistance means is interposed between said shoes and said casing closed end,

said supplemental resistance means comprising:

a pedestal received over the casing closed end boss and engaging the casing closed end between the boss and the coil spring,

a spring seat seated against the shoes within the coil spring,

and a tubular member formed from resiliently compressible material received about said bolt between said pedestal and said spring seat within and spaced from said spring,

said tubular member being of annular cross section configuration and defining a nominal outer diameter that is approximately 2 times its internal diameter,

with the outer wall ofsaid tubular member at the end of said tubular member that engages said pedestal tapering radially outwardly of said casing in the direction of said casing open end,

said tubular member being proportioned to substantially fill the space between said bolt, said spring, said pedestal and said spring seat in the compressed relation of the gear, and extend about 55 percent of the distance between said shoes and said casing closed end.

2. The improvement set forth in claim 1 wherein:

said helical spring and said tubular member in the assembled relation of said gear are each under a pressure on the order of 6,000 pounds.

3. The improvement set forth in claim 2 wherein:

said helical spring and said tubular member are proportioned such that in the compressed relation of the gear, they in combination provide a resistance pressure that exceeds the resistance pressure at initial travel by a difference on the order of 530 percent.

4. In a draft gear for mounting in the draft gear pocket of a railroad car and including a casing forming a friction chamber defining friction walls, friction sho s in sliding engagement with the walls, said casing having open and closed ends, a selfadjusting thrust member adjacent the casing open end cooperating with an articulated cluster of wedge members for transmitting load forces to the shoes, and resilient means for resisting the load response movement of said shoes including a coil spring seated between the casing closed wall and the shoes, and an assembly bolt extending axially of the gear between said thrust member and an inwardly extending boss formed in said casing closed end, the improvement wherein:

supplemental resistance means is interposed between said shoes and said casing closed end,

said supplemental resistance means comprising:

a pedestal received over the casing closed end boss and engaging the casing closed end between the boss and the coil spring,

a spring seat seated against the shoes within the coil spring,

and a tubular member formed from resiliently compressible material received about said bolt between said pedestal and said spring seat within and spaced from said spring,

said tubular member being of annular cross-sectional configuration with the outer wall surface thereof facing said spring being formed to define a cylindrical portion at the end thereof that is adjacent said spring seat and a frustoconical portion at the end thereof adjacent said pedestal and tapering from said cylindrical portion inwardly of the casing in the direction of said pedestal,

said tubular member being proportioned to substantially till the space between said bolt, said spring, said spring seat and said pedestal in the compressed relation of the gear.

5. The improvement set forth in claim 45 wherein:

said pedestal and said spring seat are respectively disposed in substantial concentric relation about the bolt and are round and have outer diameters that are substantially equivalent to the outer diameter of said cylindrical portion of said tubular member.

6. The improvement set forth in claim 5 wherein the surfaces defined by said outer diameters of said spring seat and pedestal respectively are cylindrical in configuration.

7. The improvement set forth in claim 41 wherein:

said tubular member is formed from a butyl rubber compound.

i The improvement set forth in claim 7 wherein:

said tubular member has a length in the assembled relation of the gear that is approximately 225 percent of the closure travel of the gear.

9. The improvement set forth in claim 8 wherein:

the outer diameter of said cylindrical portion of said tubular member is approximately 2.1 times the internal diameter thereof and the surface defined by said internal diameter is cylindrical in configuration substantially the full length of said tubular member. 

1. In the draft gear for mounting in the draft gear pocket of a railroad car and including a casing forming a friction chamber defining friction walls, friction shoes in sliding engagement with the walls, said casing having open and closed ends, a selfadjusting thrust member adjacent the casing open end cooperating with an articulated cluster of wedge members for transmitting load forces to the shoes, and resilient means for resisting the load response movement of said shoes including a coil spring seated between the casing closed wall and the shoes, and an assembly bolt extending axially of the gear between said thrust member and an inwardly extending boss formed in said casing closed end, the improvement wherein: supplemental resistance means is interposed between said shoes and said casing closed end, said supplemental resistance means comprising: a pedestal received over the casing closed end boss and engaging the casing closed end between the boss and the coil spring, a spring seat seated against the shoes within the coil spring, and a tubular member formed from resiliently compressible material received about said bolt between said pedestal and said spring seat within and spaced from said spring, said tubular member being of annular cross section configuration and defining a nominal outer diameter that is approximately 2 times its internal diameter, with the outer wall of said tubular member at the end of said Tubular member that engages said pedestal tapering radially outwardly of said casing in the direction of said casing open end, said tubular member being proportioned to substantially fill the space between said bolt, said spring, said pedestal and said spring seat in the compressed relation of the gear, and extend about 55 percent of the distance between said shoes and said casing closed end.
 2. The improvement set forth in claim 1 wherein: said helical spring and said tubular member in the assembled relation of said gear are each under a pressure on the order of 6,000 pounds.
 3. The improvement set forth in claim 2 wherein: said helical spring and said tubular member are proportioned such that in the compressed relation of the gear, they in combination provide a resistance pressure that exceeds the resistance pressure at initial travel by a difference on the order of 530 percent.
 4. In a draft gear for mounting in the draft gear pocket of a railroad car and including a casing forming a friction chamber defining friction walls, friction shoes in sliding engagement with the walls, said casing having open and closed ends, a self-adjusting thrust member adjacent the casing open end cooperating with an articulated cluster of wedge members for transmitting load forces to the shoes, and resilient means for resisting the load response movement of said shoes including a coil spring seated between the casing closed wall and the shoes, and an assembly bolt extending axially of the gear between said thrust member and an inwardly extending boss formed in said casing closed end, the improvement wherein: supplemental resistance means is interposed between said shoes and said casing closed end, said supplemental resistance means comprising: a pedestal received over the casing closed end boss and engaging the casing closed end between the boss and the coil spring, a spring seat seated against the shoes within the coil spring, and a tubular member formed from resiliently compressible material received about said bolt between said pedestal and said spring seat within and spaced from said spring, said tubular member being of annular cross-sectional configuration with the outer wall surface thereof facing said spring being formed to define a cylindrical portion at the end thereof that is adjacent said spring seat and a frustoconical portion at the end thereof adjacent said pedestal and tapering from said cylindrical portion inwardly of the casing in the direction of said pedestal, said tubular member being proportioned to substantially fill the space between said bolt, said spring, said spring seat and said pedestal in the compressed relation of the gear.
 5. The improvement set forth in claim 4 wherein: said pedestal and said spring seat are respectively disposed in substantial concentric relation about the bolt and are round and have outer diameters that are substantially equivalent to the outer diameter of said cylindrical portion of said tubular member.
 6. The improvement set forth in claim 5 wherein the surfaces defined by said outer diameters of said spring seat and pedestal respectively are cylindrical in configuration.
 7. The improvement set forth in claim 4 wherein: said tubular member is formed from a butyl rubber compound.
 8. The improvement set forth in claim 7 wherein: said tubular member has a length in the assembled relation of the gear that is approximately 225 percent of the closure travel of the gear.
 9. The improvement set forth in claim 8 wherein: the outer diameter of said cylindrical portion of said tubular member is approximately 2.1 times the internal diameter thereof and the surface defined by said internal diameter is cylindrical in configuration substantially the full length of said tubular member. 